Method of temperature compensation for interleaver

A method for configuring a temperature insensitive optical retarder comprising the steps of;

• providing a first wedge shaped birefringent crystal;
• providing a second wedge shaped birefringent crystal;
• providing a mount including a first material having a first thermal expansion coefficient and a second material having a second material;
• mounting the first birefringent crystal to the first material and the second birefringent crystal to the second material, so that they are movable relative to each other;
• wherein the first and second materials are selected so that the total retardance by the first and second crystal is substantially the same at a given wavelength over a given temperature range.

An optical interleaver/deinterleaver for multiplexing two data streams into a stream of channels or for demultiplexing a stream of channels into two sets of data streams comprising;

• a. at least a first and a second wedge shaped birefringent crystals each having non parallel faces;
• and
• b. a holding means for mounting said first and second birefringent crystals comprising a first material having a first thermal expansion coefficient and a second material having a second thermal expansion coefficient which is different from the first thermal expansion coefficient;
• wherein the first and the second wedge shaped birefringent crystals are attached onto the first and second materials, respectively, so that the total retardance by the first and second birefringent crystals at a first temperature is substantially the same as that at a second different temperature at a given wavelength.